1. Field of the Invention
The present invention relates to a display apparatus used in a display of a terminal of an information apparatus, such as a computer, a television set, or a mobile phone, and to a construction of a backlight used therefor.
2. Description of Related Art
For example, in color display apparatuses that have hitherto used liquid crystal, one pixel is divided into color pixels corresponding to each of the colors red, blue, and green in a manner similar to a color CRT, color filters corresponding to each color pixel are simultaneously formed and illuminated from the back by a white backlight, and each of the colors are simultaneously displayed so as to display the color of one pixel. According to this method, however, since one pixel is divided into three, the aperture ratio of the pixel decreases thereby giving a dark display, a number of signal drivers for driving liquid crystal panels corresponding to the number of colors are required, and color filters as fine as the color pixels are required, resulting in an increase in cost.
Thus, as disclosed in Japanese Unexamined Patent Publication No. 5-19257, a color display apparatus is proposed in which a multicolor backlight is combined with light valves. According to this construction, one pixel is not divided into each of the colors red, green, and blue. Therefore, when, for example, an active matrix panel is used, since the number of active elements to be formed on the whole of the panel is reduced to one-third, the yield is increased, the aperture ratio of one pixel increases to give a bright display, the number of signal drivers is reduced to one-third of that in a conventional display apparatus, and the cost can be reduced because the color filters are not required.
In a construction using cold-cathode tubes, Japanese Unexamined Patent Publication No. 5-19257 discloses an arrangement in which red R, green G, and blue B cold-cathode tubes and light guide plates to be paired therewith are stacked, and discloses a driving method. Japanese Unexamined Patent Publication Nos. 5-264988 and 5-346570 disclose a construction in which three R, G, and B cold-cathode tubes are arranged on one end surface of a sheet of a light guide plate, and a construction in which light from one white illuminant is converted into R, G, and B time-divided light by R, G, and B filter shutters. Japanese Unexamined Patent Publication No. 6-67149 discloses a construction in which three R, G, and B cold-cathode tubes are arranged on the back of a panel, and a driving method therefor. In particular, voltages supplied to the backlights of each color are independently controlled so that the colors are balanced. As an R, G, and B switching backlight, Japanese Unexamined Patent Publication No. 6-301004 discloses a combination of a white light source, R, G, and B color filters, a liquid crystal shutter, and a diffusing plate. Japanese Unexamined Patent Publication No. 6-301032 discloses a combination of R, G, and B light sources and a liquid crystal shutter. Japanese Unexamined Patent Publication No. 9-101497 discloses a driving method for a gray-level display using TN-mode liquid crystal light valves and the above construction. In Japanese Unexamined Patent Publication No. 9-114421, in a construction using a TFT element, clear display is obtained by resetting the state of a liquid crystal when an image signal is to be rewritten.
On the other hand, Japanese Unexamined Patent Publication No. 3-187192 discloses the use of an organic EL, which is thin, ad has low power consumption, as a backlight source of a conventional direct-view-type color display apparatus.
According to the above-described conventional techniques, when a light source, such as a cold-cathode tube, is used as a multicolor backlight, the outer shape of the display apparatus is large, the cost is high because of a complicated driving circuit, and the backlight consumes much power and cannot be used in a portable information apparatus.
In Japanese Unexamined Patent Publication No. 3-187192 using the organic EL for the backlight, since R, G, and B EL devices are simply arranged instead of color filters of a conventional color liquid crystal panel, as many pixels as in the conventional display apparatus are required, and the number of drivers is about equal to that in the conventional display apparatus. Therefore, the cost is high and the aperture ratio is low.
The present invention has been achieved in consideration of the above problems, and an object is to provide a multicolor light source having a simple structure and a simplified driving circuit, and to provide a display apparatus using the light source which is compact, has low power consumption, and is inexpensive.
According to the present invention, there is provided a display apparatus that may include a planar optical modulation panel; and
a surface light source arranged on the back of the planar optical modulation panel, and having at least a first luminescent region including a luminescent material emitting light with a first color and a second luminescent region including a luminescent material emitting light with a second color different from the first color in a surface substantially parallel to a surface of the planar optical modulation panel;
wherein one scanning period of a color image to be displayed is divided into the number of luminescent colors of the surface light source, each of the luminescent regions is allowed to emit light in accordance with each of the divided periods, brightness information of the luminescent color of the emitted light is formed by the planar optical modulation panel in synchronism with the periods, and light of each color is optically modulated to perform color display.
Furthermore, according to the present invention, there is provided a display apparatus that may include
a planar optical modulation panel; and
a surface light source arranged on the back of the planar optical modulation panel, and having at least a first luminescent region including a luminescent material emitting light with a first color and a second luminescent region including a luminescent material emitting light with a second color different from the first color in a surface substantially parallel to a surface of the planar optical modulation panel, and the first luminescent region and the second luminescent region have a spiral form.